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AIDS is caused by the human immunodeficiency virus (HIV). HIV attacks particular cells of the victim's immune system. As a result, the person's immune defenses are weakened tremendously, and the victim is unable to fight off infections. Even worse, the victim is left vulnerable to many serious diseases, such as tuberculosis, pneumonia, fungal infections, and cancer. Death usually occurs as a result of one of these diseases.


The economic cost of the AIDS epidemic is staggering. First, there is the cost of caring for one patient with AIDS. The most common treatment in the United States is a "cocktail," or mixture, of drugs that can cost up to $15,000 per patient per year. These drugs slow the progress of the disease, but do not eliminate HIV from the patient's body. Research also shows that these drugs must be taken regularly from the time of diagnosis for the rest of the patient's life: As soon as the drugs are stopped, the virus bounces back, as dangerous and life-threatening as ever. A further drawback is that the virus in a patient may become resistant to these drugs.

In the United States alone, the cost of providing these drugs to AIDS patients is in the millions of dollars and is rising each year. Unfortunately, developing nations cannot afford to treat their HIV-infected citizens with these drugs. African nations have an average of $10 per year per person for medical care, yet Africa is the part of the world that is hardest hit with the disease.

The epidemic has other costs, too. In some countries, such as Uganda, Zambia, and Zimbabwe, three-fourths of the hospital beds are filled with children who are HIV-positive. Millions of adults have died, and many of them have left orphaned children. Many others have left surviving spouses who also are ill, need treatment, and cannot work. Families cannot find money to pay for funerals, and employers must find and train new employees. This problem is eating away at these countries' economies.

As one scholar described the problem, "The epidemic's direct and indirect consequences are wiping out the gains that many of these countries have made in the past 30 years."

AIDS—Death Rate

The total number of worldwide deaths from AIDS in 1998 was estimated to be 2.5 million (2 million adults and 510,000 children under the age of 15).

The total number of worldwide deaths since the beginning of the epidemic is estimated to be 13.9 million (10.7 million adults and 3.2 million children under the age of 15).


AIDS, acquired immune deficiency syndrome, is a disease in which the immune system no longer functions effectively. It is caused by the human immunodeficiency virus (HIV). People with AIDS are vulnerable to a variety of other diseases (opportunistic infections) that only rarely occur in people with healthy immune systems.


If a person is infected with HIV, his or her body will make antibodies, special proteins produced by the immune system that recognize and can attach to HIV. To test for HIV infection, doctors look for these antibodies in the person's blood. If antibodies against HIV are present, they are evidence that the person is infected with HIV. If antibodies against HIV are not present, the person either is not infected or was infected recently enough that his or her body has not yet made these antibodies in detectable quantities. Only another test at a later date can distinguish between these possibilities.

Infection with HIV is not the same as having AIDS. When a physician suspects that a person may have AIDS, he or she may order another laboratory test of the person's blood. The diagnosis of AIDS is confirmed if the person's CD4 T-cell concentration is lower than 200 cells per cubic millimeter of blood (normal levels are at least 800 cells per cubic millimeter of blood), or if the person develops one or more of the opportunistic infections associated with AIDS.

AIDS—Incidence (Predictions)

Scientists are predicting that in the short term, the international epidemic of AIDS will become worse, especially in the developing countries of Africa and Southeast Asia. The spread of the epidemic means that the already enormous burden of caring for the ill will only increase.

In contrast, scientists are predicting that in the United States and other industrialized countries, the epidemic will slow, at least for some populations. HIV infection, however, likely will continue to rise in certain populations (especially the poor and disadvantaged).

The cost of care will also rise significantly, as more people who today are HIV-positive develop AIDS.

Graph depicting changes in HIV diagnoses among Whites, African-Americans, and Hispanics

AIDS—Incidence (United States)

In the United States, there are more than 1 million people who are HIV-positive. Each year, approximately 50,000 more people are infected, including about 2,500 infants. AIDS is now the leading cause of death for men between the ages of 25 and 44, and the fourth highest cause of death for women in this age category.

Whereas the death rate from AIDS and the rate of HIV infection are declining overall in the United States and other industrialized countries, it is not declining—and, in some cases, may be increasing—among certain groups of people, including teenagers, women, and people over the age of 50.

AIDS—Incidence (Worldwide)

More than 40 million people worldwide have contracted the human immunodeficiency virus (HIV) since the early 1980s, and nearly 14 million have died of AIDS. About 28 million people currently have AIDS or are infected with HIV, and about 16,000 more people are infected with HIV every day. In 1998 alone, an estimated 2.5 million people died of AIDS, 510,000 of them children.

Worldwide, the highest incidence of HIV infection is in sub-Saharan Africa. Two-thirds of all HIV-positive people and 90 percent of all infected children live in this area. In some African countries, 1 in 4 adults is HIV-positive. The second highest incidence of HIV infection is in Southeast Asia. Here, the epidemic is worst in India and Thailand.

AIDS—Modes of Infection

You can get HIV (the virus that causes AIDS) from any person who is infected with the virus, even if he or she does not look sick, does not know he or she is sick, and does not yet test positive for the virus (is not yet HIV-positive).

Most people get HIV by

There are no known cases of someone getting HIV through contact with an infected person's tears or saliva, but it is possible to catch HIV through oral sex, especially if you have open sores in your mouth or bleeding gums.

In the past, some people were infected with HIV from getting a blood transfusion from an infected person. Today, the blood supply is carefully tested, and the risk of infection from a blood transfusion in the United States is very low.


The name "AIDS" means "acquired immune deficiency syndrome."

The word "acquired" means that a person can catch AIDS, that is, that it is an infectious disease.

The words "immune deficiency" mean that the disease causes a weakness in a person's immune system. The immune system is the part of the body that fights disease.

The word "syndrome" is a medical term for a group of health problems that all are associated with a particular disease. People with AIDS display many health problems, such as weight loss, problems with infections, brain tumors, and other health problems.

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